Morphological and histochemical changes occurring in mammalian lenses during development of hereditary and senile cataracts are to be studied. Histochemical localization of acid hydrolases and transport enzymes shoud help to elucidate the regional lens changes leading to cataract formation. Specimens used in this study will be obtained from laboratory animals and humans. Slit lamp analyses will be used to establish the clinical stage of each cataract prior to removal of the lens for light microscopy and electron microscopy.